The detection of pathogen, protein, and nucleic acid targets in biological samples forms the basis of the multi-billion dollar in vitro diagnostic industry. Detection of protein and nucleic acid targets can be divided into diagnostic and research based markets. The diagnostic market includes the detection and identification of pathogens such as viruses and bacteria, the identification of various genetic markers, and the identification of markers associated with the presence of tumors. The research market includes the genomics and proteomics industries, which require analytical, drug discovery, and high-throughput screening technologies.
The ability to diagnose patients at the “point of care” is expected to yield major savings to the health care industry and improve the effectiveness of treatment. For example, “point of care” testing is a requirement for the effective use of anti-influenza drugs such as RELENZA and TAMIFLU. This means that the diagnoses of influenza virus infection must be made while the patient is in the doctor's office. Recent studies in the United States indicate that that when ZSTATFLU, a rapid, influenza virus diagnostic assay was used at the point of care, healthcare costs were significantly reduced by elimination of inappropriate treatment and the timely initiation of effective therapy. As another example, the advent of personalized medicine will require genetic screening of individuals at the point of care to determine whether the individual is a candidate for particular treatment strategies or will have an adverse reaction to the preferred medication.
Currently used diagnostic assays include radioimmunoassay (RIA), enzyme-linked immunosorbent assay (ELISA), agglutination assays, surface plasmon resonance (SPR), and polymerized multilayer assemblies for the detection of receptor-ligand interactions (Charych et al., Science 261:585 (1993); Pan et al., Langmuir 13:1365 (1997)). However, most of these method requires expensive reagents (e.g., radioactively labeled antibodies or antigens), are not adaptable to microarray format (e.g., agglutinations assays), or require expensive, laboratory based equipment (e.g., SPR).
Although many of the conventional assay methods described above work very well to detect the presence of target species, they are expensive and often require instrumentation and highly trained individuals, which makes them difficult to use routinely in the field. Thus, a need exists for assay devices and systems which are easier to use and which allow for evaluation of samples in remote locations.